[B43]: Use input-polldev for the rfkill switch

This removes the direct call to rfkill on an rfkill event
and replaces it with an input device. This way userspace is also
notified about the event.

Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>